The present invention relates to powder-compacting apparatus and method and, more particularly, to an apparatus and method producing compacted articles within very close dimensional tolerances, with uniform density, and with sharp edges. A particular application for which the present invention is specifically well suited is the production of indexable throwaway cutting inserts for cutting tools, made of powder metals and metal alloys which, after sintering, requires very little grinding, if any, of the cutting edges and tips.
The present invention is concerned with improved tooling for use in powder-compacting presses such as are disclosed in U.S. Pat. Nos. 3,826,599, 3,775,032, 3,730,659, 3,726,622, 3,645,658, 3,574,892, 3,561,056, 3,516,142, 3,344,213 and 3,328,840, all of which are assigned to the same assignee as the present application.
In the powder-compacting presses disclosed in the aforementioned U.S. Patents, articles are compacted and formed in a single- or multi-cavity die forming part of a punch and die set, with the finished articles being automatically ejected from the die cavities, picked up by a vacuum pick-up head, and conveyed into suitable receptacles. A work station positioner assembly, which is part of the press, is mounted linearly or angularly movable transversely over the die plate. The work station positioner carries a powder dispenser, an anvil and the pick-up head. The powder dispenser, which is supplied with powder from a primary powder supply connected thereto by means of a flexible tubing or the like, is first positioned over the die cavity or cavities which are thus filled with powder as the punches are displaced dowwardly so as to draw a predetermined amount of powder into the die cavity or cavities. The dispenser is then removed from above the die cavity or cavities by the subsequent motion of the station positioner assembly, and the anvil is, in turn, positioned over the die cavities. The anvil is clamped over the die cavity by means of a pivotable clamp supported above the anvil and is acutated in timed relation with the movement of the punches. The anvil is held down with sufficient pressure to permit the compaction of the powder against the anvil as a result of an upward motion of the punches into the die cavity of cavities. The anvil is then removed from its position over the die cavity or cavities and is replaced by the pick-up head as a result of a further linear or angular motion of the work station positioner transversely across the face of the die plate. The punches are displaced upwardly so as to being their upper ends in substantial flush alignment with the upper surface of the die plate, such that the finished compacted articles are ejected from the die cavities and picked up by the pick-up head. As the result of a return linear or angular motion of the work station positioner to the initial fill position, the pick-up head is removed from over the die cavity and is disposed over one or, if a plurality of die cavities are employed, a series of discharge apertures arranged in a disposition similar to the arrangement of the die cavities in the die plate, and the finished compacted article or articles are drawn, as by vacuum, through the discharge aperture or apertures into a container or separate containers.
Alternatively, the compacted articles are drawn directly into the pick-up head by suction and transported to a remote discharge station by way of tubular conveyors through which the compacted articles are propelled by suction, or a flow of air, or a combination of both.
In U.S. Pat. Nos. 3,775,032, 4,047,864, 4,061,452 and 4,061,453, tooling arrangements for compacting articles from powder material are described in which a mold cavity is defined partly by the end face of an upper punch projecting through an anvil element above the die cavity, partly by the die bore wall and partly by the end face of the lower punch.
The present invention is an improvement on the tooling arrangements disclosed and claimed in the aforesaid patents which permits to obtain compacted articles, generally of a prismatic or pyramidal shape and having remarkably sharp edges. The forming of sharp edges is an advantageous feature where such sharp edges are desirable, as is the case when compacting powder metals and powder alloys are used for forming a "green" cutting tool insert or bit which is subsequently sintered to a solid mass of ultra-hard material.